There is no excuse for a cyclist hitting a pedestrian in a crosswalk, especially when traffic has stopped for the pedestrian. The kinetic energy of a cyclist can mean serious injury to a pedestrian. Cyclists have to take care to make sure that they don't put pedestrians in jeopardy -- or even cause anxiety with close calls.

This totally happens at my kids' school crossing. The cops stop the cars, and presumably the bikes, so the kids can cross the street, but half the cyclists think they can keep going and zoom right past the cop, weaving between me and the kids.

I'm pleased that you are paying attention to this problem! As someone who to Newton Centre every morning and back every night, I can tell you that the cars are bad enough (I've been hit twice since Labor Day by cars "creeping" forward at stop signs), but the bikes can be rough too. They love to run through the light at Centre and Gibbs/Bowen St. in the morning, even when the light is red and the crossing guard has stopped traffic. I even had one pleasant fellow on his bike tell me to "stay on the f***ing sidewalk." I wish the city would expend some effort enforcing the law for drivers, but also for bikers.